gistfile1.cs

Transform target;
float rotateSpeed = 10;
// Use this for initialization
void Start () {
	// 將 target指定名稱為Imege的物件，並取得物件的Transform
	target = GameObject.Find("Image").GetComponent<Transform>();
}
	

void Update () {
	Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
	RaycastHit hit;
	Physics.Raycast(ray, out hit);
	Debug.Log("This hit at " + hit.point );
	Vector3 pos;
	pos = hit.point;
	pos.z = 0;	// 忽略z軸
	float angle = Vector3.Angle( pos - target.position, Vector3.down);
	if(pos.x > target.position.x)	{
		angle*=-1;
	}
	target.rotation = Quaternion.Slerp(target.rotation,Quaternion.Euler(0,0,180-angle),rotateSpeed*Time.deltaTime);
}